Carbon-grain cells of telephone-transmitters.



0. E. EGNLR & J. G. HOLMSTRUM.

CARBON GRAIN CELLS 0F TELEPHONE TRANSMITTBRS- APPLICATION IILI-ID NOV.2, 1910.

1,042,772. Patented Oct. 29, 1912.

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COLUMBIA PLANOGRAPH CD-IWASMINOTON. D. c.

UNITED STATES PATENT OFFICE.

CARL EMIL EGNER, or STOCKHOLM, AND JOHAN GUNNAR HoLMsTn'oM, orsAL'rsJos'roRANGEN, SWEDEN.

CARBON-GRAIN CELLS OF TELEPHONE-TRANSMITTERS.

Specification of Letters Patent.

Patented Oct. 29, 1912.

Application filed November 2, 1910. Serial No. 590,335.

To all whom it may concern:

Be it known that we, CARL EMIL EcNiiR, a subject of the King of Sweden,and resident of Blekingegatan 63, Stockholm, in the Kingdom of Sweden,and JOHAN GUNNAR Homrs'rnoir, a subject of the King of Sweden, andresident of Saltsjo-Storangen, in the Kingdom of Sweden, have inventedcertain new and useful Improvements in Carbon-Grain Cells ofTelephone-Transmitters, of which the following is a specification,reference being had therein o the accompanying drawing.

This invention relates to telephone transmitters of that class, whichare provided with a plurality of stationary electrodes,each forming thebottom of a transmitter cell, and with a diaphragm common to all cells,and the object of the invention is to so arrange the said transmittersthat the rings or walls containing the cells can adjust themselvesautomatically into the right position with relation to the stationaryelectrodes respectively without causing any disturbing strain of theparts of the transmitter. This object is gained by using a disksupported in a yielding manner and provided with openings through whichthe stationary electrodes project, the said disk forming a support tothe said rings or walls in such a manner as to allow them to slide onthe disk.

In the accompanying drawing, Figure 1 is a vertical section of atransmitter provided with a plurality of carbon-grain cells arranged inaccordance with this invention, Fig. 2 is a front view of thetransmitter, and Fig. 3 is a section of one of the cells on a greaterscale.

The transmitter shown in the drawing is adapted especially for strongcurrents when a comparatively strong heating of the cells is to befeared.

A is the diaphragm carrying an electrode 15. The stationary electrodes3, 4, 5, and 6, are fixed to a wall 7 of a casing 8 containing a coolingliquid 1. Openings are provided in a light disk 2 of mica, aluminium orthe like common to all the electrodes, through which openings theelectrodes project. The said openings are so great, that nocarbon-grains having passed out from the cell, can be jammed between theelectrode and the disk. The disk 2 is held in proper position and at asuitable distance from the plane, in which the front faces of thestationary electrodesare located, by guide pins 9, fixed in the wall'l,spiral spring 10, wound around the said pins, and bearing against therear side of the disk, and nuts 11 in screw threaded engagement with thepins and bearing against the front side of the disk.

The cell proper is inclosed by a ring 12 of asbestos or any othersuitable material, which can endure a high temperature with out beingdamaged. The inner diameter of the ring is very much greater than theouter diameter of the electrode. The said ring 12 bears against a thinring 13 of felt, located in and bearing against the bottom of a thinbowl 17 'of aluminium, which in its turn bears against the disk 2, afurther ring 1% of felt being preferably mounted between the said bowland the disk. The main object of the rings 13 and 14 is to formtightening means around the electrode and prevent carbon-grains fromfalling out and for that purpose they fit snugly t0 the same. The frontend of the asbestos ring 12 bears against the diaphragm or, as shown inthe drawing, against the electrode 15 fixed to the same in a suitablemanner and oscillating with the same. Such an electrode can be providedat each cell.

The pressure of the asbestos rings 12 against the oscillating electrode15 is adapted by suitably adapting the tension of the spiral springs 10.The said pressure may not be too great as it will then damp theoscillations of the diaphragm a too great extent, but it may, however,be not too slight, as the own oscillations of the diaphragm then becometoo effective.

Owing to the fact that the soft felt rings 13 and 14: are locatedbetween the hard asbestos ring 12 and the disk 2 the damping of theoscillations of the diaphragm does not become too great even if thepressure against the electrode 15 should be comparatively great.

A thin ring of asbestos may, if wanted, be substituted for the felt ring13, and, possibly, for the ring 14. The effect of the transmitter is,however, reduced by the said arrangement, owing to the fact that thecarbon-grains would have the tendency to be jammed between the saidasbestos ring and the electrode, the pressure between the ring 12 andthe electrode 15 being, besides, not so elastic as in the arrangementshown in the drawing.

The diameter of the openings provided in the bottom of the aluminiumbowls 17 and the disk 2 is very much greater than the diameter of theelectrodes. Consequently, if carbon-grains should enter the space, between the felt rings 13 and 14 and the electrode, it is not to be fearedthat they are jammed. The said grains may, even, work themselves out ofthe cell gradually the said way without any considerable disadvantagesbeing thereby created.

A felt ring may be substituted for the asbestos ring 12, but thetransmitter is then not able to bear a strong current, as the said feltring is easily burned, especially at the electrode 15.

By means of the disk 2 and the spiral springs 10, acting upon the same,all the asbestos rings 12 are forced forward against the electrode 15 ata pressure as uniform as possible and without being able to occupy anoblique position. As the four asbestos rings and the parts cooperatingwith the same are entirely independent one of the other, they can slideon the disk 2 and be centralized with regard to the electrodesrespectively, owing to which fact no accidental variations of theresistance and consequently the tension in the cells can be effected, bylateral forces.

The arrangement of the cell described above is suitable especially fortransmitters provided with two or more cells for causing the cells toact simultaneously and in unison.

WVhat we claim is:

1. In a telephone transmitter the combination of a plurality ofstationary electrodes, each forming the bottom of the transmitter cellsrespectively, a diaphragm common to the cells, a disk supported in ayielding manner and provided with openings through which the electrodesextend, and inclosing walls for the cells, bearing against the said diskin a slidable manner, substantially as described and for the purpose setforth.

2. In a telephone transmitter the combination of a plurality ofstationary electrodes, each forming the bottom of the transmitter cellsrespectively, a diaphragm common to the cells and carrying a number ofelectrodes, closing the cells, a disk supslidable manner, substantiallyas described and for the purpose set forth.

In witness whereof, we have hereunto signed our names in the presence oftwo subscribing witnesses.

CARL EMIL EGNER. JOHAN GUNNAR HOLMSTROM.

Witnesses HEDING MELINDER, Ronnn'r APELGREN.

Copies of this patent may be obtained for five cents each, byaddressing" the Commissioner of Patents, Washington, D. G.

